This invention relates to a crankshaft angle sensor for an internal combustion engine.
FIG. 5 is a sectional side view of a known crankshaft angle sensor for an internal combustion engine in which a housing 5 is made of a resin and disposed within a distributor assembly (not shown) for an internal combustion engine (not shown). The housing 5 is a substantially disc-shaped member having a central bore 5a through which a distributor rotary shaft 1 extends. A signal disc plate 2 is mounted to the rotary shaft 1 by means of a blank 12 and has a slit 2a disposed at its edge. The rotary shaft 1 is rotatably supported within the distributor assembly (not shown) and adapted to be connected to a camshaft (not shown), which is connected to an engine crankshaft (not shown), for synchronous rotation therewith.
The housing 5 also has a vertically rising portion 5e having a bore or a first chamber 5b therein which extends through the entire length of the housing 5 including the rising portion 5e of the housing 5. The first chamber 5b has an upper cavity 5j, a lower cavity 5i and a relatively narrow, reduced-diameter, comparatively long neck portion 5f formed at the middle portion thereof. Disposed within the neck portion 5f is an angle sensing element 13 hermetically attached thereto by for example a bonding agent. The angle sensing element 13 comprises a light emitter element 3 and a light detecting element 4 which faces to the light emitter element 3 for detecting a light emitted from the light emitter element 3.
A plurality of insert conductors 6 are disposed within the lower cavity 5i of the first chamber 5b. The insert conductors 6 extend vertically and downwardly, as illustrated in FIG. 5. The light emitter element 3 and the light detecting element 4 respectively have leads 3a and 4a each electrically connected by for example resistance welding method to the insert conductors 6 individually. As seen from FIG. 5, as the light emitter element 3 is remote from the insert conductors 6 separating by the light detecting element 4, the lead 3a of the light emitter element 3 is bent into a substantially U-shape and its one end is relatively longer than the other. The lead 3a passes through the upper cavity 5j and a through hole 5d which extends through the housing 5 from the upper cavity 5j to the lower cavity 5i in parallel with the neck portion 5f of the first chamber 5b. The leads 3a and 4a are connected to the insert conductors 6 by means of connection portions which extend vertically downward.
The rising portion 5e also has a groove 5g disposed in a side surface 5h which faces the rotary shaft 1 between the light emitter element 3 and the light detecting element 4. The disc plate 2 including a slit 2a rotates synchronously with the rotary shaft 1 and passes through the groove 5g for the purpose which will become apparent later. Hermetically attached to both opening portions of the upper cavity 5j and the lower cavity 5i of the first chamber 5b are covers 10 and 11 for preventing harmful gas outside from entering into the first chamber 5b.
As illustrated in FIG. 5, the housing 5 also has a second chamber 5c mounting a circuit board 7 having an electronic circuit thereon. The electronic circuit includes a power circuit portion for the light emitter element 3 and a wave-form analysis circuit portion for analyzing output signals from the light detecting element 4. The electronic circuit on the circuit board 7 is electrically connected to the light emitter element 3 and the light detecting element 4 through the insert conductors 6 disposed in the housing 5.
The circuit board 7 also has a plurality of leads 8 electrically connecting the electronic circuit thereof to outer terminals 14 disposed in the housing 5 for external connection. The leads 8 and the outer terminals 14 have connection portion which are bent and extends vertically downwardly and electrically connected each other by a resistance welding method. The height of the second chamber 5c of the housing 5 therefore becomes inevitably large in order to accommodate the vertically extending connection portion. The circuit board 7 is covered with a resin 15 which is for example comparatively soft silicone for preventing an ambient moisture and promoting a radiation of heat. The cover 9 is hermetically attached to an opening portion of the second chamber 5c for preventing harmful gas outside from entering into the second chamber 5c.
In the above known crankshaft angle sensor, when the rotary shaft 1 rotates synchronously with the camshaft (not shown) connected to the engine crankshaft (not shown) of the internal combustion engine (not shown), the disc plate 2 also rotates synchronously. The disc plate 2 including the slit 2a formed therein passes between the light emitter element 3 and the light detecting element 4 to intermittently interrupt the light beam emitted from the light emitter element 3. The light detecting element 4 detects the intermittent light beam and provides to the electronic circuit of the circuit board 7 an output signal indicative of the crankshaft rotational speed and/or position in response to the intermittent light beam. The electronic circuit of the circuit board 7 shapes a wave-form of the output signal provided by the light detecting element 4 with a comparator thereof and converts its impedance and provides a pluse signal to the outer terminal 14 through the lead 8 of the circuit board 7. As the camshaft connected to the rotary shaft 1 rotates at a fixed ratio in respect to the rotation of the engine crankshaft (not shown), a crank angle of the engine crankshaft can be detected by counting the pluse signals provided by the electronic circuit of the circuit board 37. An ignition timing of the internal combustion engine (not shown) can be therefore controlled adjustedly as is well-known in the art.
In the known crankshaft angle sensor as described above, the light emitter element 3 is remote from the insert conductors 6 because it is separated by the light detecting element 4. Further, the light emitter element 3 and the light detecting element 4 are disposed within the first chamber 5b and, on the other hand, the circuit board 7 is disposed within the second chamber 5c which is separated from the first chamber 5b in the radial direction of the rotary shaft 1. Therefore, the overall dimensions of the sensor are large. Connecting conductors such as the lead 3a of the light emitter element 3 and the insert conductors 6 should be long. The longer such connecting conductors are, the more sensitive the crankshaft angle sensor are to an outside electrical noise and there are a lot of electrical noises in the inside of the distributor assembly (not shown) and the noises are easily piled up on such long connecting conductors. Moreover, the output impedance of the light detecting element 4 is increased with a longer lead.
Further, as the lead 3a of the light emitter element 3 must be bent in a complex shape such as a substantially U-shape whose one leg is longer than the other and the longer leg must be inserted into the through hole 5d formed in the housing 5 and electrically connected to the insert conductor 6, it is difficult to automatically assemble the crankshaft angle sensor and assembly processes are not efficient.
Also, since the first and second chambers 5b and 5c as well as the lower cavity 5i for accommodating the vertically extending connection portion between the lead 3a and the insert conductor 6 are necessary, the height of the housing 5 becomes inevitably large, so that the known crankshaft angle sensor can not be compact. Further, as the lead 3a of the light emitter element 3 is so long that a form of the lead 3a is not stable, it is difficult to securely connect the lead 3a to the insert conductor 6 and the connecting portion therebetween may come off. Still further, stresses caused by repeated violent temperature changes are concentrated on the connecting portion between the lead 3a and the insert 6. Therefore the connecting portion therebetween may be cracked and damaged easily, resulting in a poor reliability.
The long lead 3a is made for example of Fe-Ni alloy such as Kovar (Trade Name) plated with gold which is very expensive. The known crankshaft angle sensor is not economical.